Drop the 300SD rear end - Page 2 - PeachParts Mercedes-Benz Forum

Maxbumpo · #16 02-02-2015, 11:29 AM

Heed this!!!

Quote:

Originally Posted by vstech

Oh... Each axle stub will have a set of spacers on them where they go into the diff... Be sure to keep them on the side they came off of...

steeleygreg · #17 02-03-2015, 12:33 AM

Made some progress tonight. Sub Frame dropped out of car and moved out from under car. It took some manipulation and prying differential away from driveshaft, but it finally broke free. Inspection of sub frame shows rust towards outer wing on each side and on both top and bottom. Media blasting will probably get rid of the rust, then prime and Rino-liner.

Stretch · #18 02-03-2015, 02:44 AM

Are you going to replace the trailing arm bushings?

steeleygreg · #19 02-03-2015, 06:07 AM

Currently I don't know. I looked at two which I can see at the moment and the rubber didn't seem to look old and cracked. Stretch I've read the threads from you and whiskey Dan on replacing these and the procedure does not seem to be difficult. How do you tell if they are bad ? What is the indicator ?

I have new trailing arm bushings for a 123. I assume they're the same bushings for the trailing arms are the same between a 123 and a 126. The subframe is different between the two frame types.

Stretch · #20 02-03-2015, 07:26 AM

Quote:

Originally Posted by steeleygreg

Currently I don't know. I looked at two which I can see at the moment and the rubber didn't seem to look old and cracked. Stretch I've read the threads from you and whiskey Dan on replacing these and the procedure does not seem to be difficult. How do you tell if they are bad ? What is the indicator ?

I have new trailing arm bushings for a 123. I assume they're the same bushings for the trailing arms are the same between a 123 and a 126. The subframe is different between the two frame types.

I'm pretty sure the W126 trailing arm bushings are the same as the W123 ones. These should be 126 352 01 65

The only different variants I have heard about are special off centre ones that used to be sold by fastlane so you could adjust the camber (I don't think the Pelican sells these though) - and besides that's not a problem for you is it?

It is difficult to check the integrity of the trailing arm bushings. Try clamping the subframe and then try pushing the trailing arms at the hubs in towards the differential and in the opposite direction. If you can get someone to do this whilst you look at the bushings cracks or gaps might be easier to see. If you (as human) can feel any great movement at the hub whilst doing this check I imagine they are shot and should be replaced - just imagine what it would be like on two wheels Starsky and Hutch stylee...

...I'm sympathetic to the attitude "change 'em whilst the subframe is out" - however I'm also sympathetic to the evidence that "new parts aren't necessarily better than the ones already fitted to the car" => As always this is going to have to be based on your gut feeling of what you find

fahrvergnugen · #21 02-03-2015, 09:00 AM

Don't all W126s have SLS? If so, does your car 'raise' after starting? If so, I would say your bushings need to be replaced. Bergsma states that if there is movement in the SLS after starting, replace the bushings, diff mount, etc., until it no longer raises.

Also might help if you had a rear-side view of your car before you began this repair, as in is there rear-sag?

As for me, I have a newer diff mount installed, and yet when the car starts it raises a good 1.5-2", and needs to come up more. I Want to do this repair, but I live in a Townhouse just now, and have limited tools... :-(

vstech · #22 02-03-2015, 09:12 AM

Quote:

Originally Posted by fahrvergnugen

Don't all W126s have SLS? If so, does your car 'raise' after starting? If so, I would say your bushings need to be replaced. Bergsma states that if there is movement in the SLS after starting, replace the bushings, diff mount, etc., until it no longer raises.

Also might help if you had a rear-side view of your car before you began this repair, as in is there rear-sag?

As for me, I have a newer diff mount installed, and yet when the car starts it raises a good 1.5-2", and needs to come up more. I Want to do this repair, but I live in a Townhouse just now, and have limited tools... :-(

No.
Very rare to find an SD with SLS... I'm not saying it's impossible they are out there... But I've never seen one.

SD Blue · #23 02-03-2015, 01:17 PM

I agree with Stretch. It is difficult to determine the condition of the subframe bushings without removing them. If you find one that is marginal, it is pretty easy to change them all. Fairly inexpensive as well.

Finding worn subframe bushings on mine, I think contributed to rear wheel bearing wear as well.

Once you change them, you will be amazed at the difference!

steeleygreg · #24 02-03-2015, 09:27 PM

Gentlemen, I agree with your assessment of the trailing arm bushings. If you've gone down to this level, replace bushings makes sense and that's what will be done. This is turning into a true R&R. SOOOOO next is to seperate the trailing arms from the sub frame, clean parts, have media (soda blast) sub frame, trailing arms, prime and POR15 / Rino liner parts. Next is to install new bushings and then re-install.

steeleygreg · #25 02-03-2015, 09:38 PM

Got some work done tonight. Goal was to get the sub frame and trailing arm assembly on a work surface table so as to save my aging bad back. First we tried lifting the assembly minus differential, but according to my helper (12 yr old son) he said it was to heavy. Since my wife was at work and my other son was out with his girlfriend I needed another plan.

So, going to plan "B" I decided to use leverage.
I strapped a rope around the sub frame assembly and lifted up and leverage onto a rolling table. Worked nice....... and I didn't get a herniated disc.

steeleygreg · #26 02-03-2015, 10:23 PM

Once assembly is on the table was to, we rolled it to the other side of the garage. Since their about 5 engines, a bunch of wood working equipment and various other junk, room is a little tight.

In the picture of the coil pertch, one of the bolts threads is left from removing the shocks. Apparently this is par for the course for suspension components. I'll either drill it out or maybe weld some threaded rod and heat the nut with Acetylene.

steeleygreg · #27 02-03-2015, 10:34 PM

I found the reason why the emergency brakes wouldn't work. Investigation showed why !

In the pic of the differential, can someone tell me what this electrical connector on the differential is and what is it for ?

Stretch · #28 02-04-2015, 03:04 AM

Quote:

Originally Posted by steeleygreg

O...
In the picture of the coil pertch, one of the bolts threads is left from removing the shocks. Apparently this is par for the course for suspension components. I'll either drill it out or maybe weld some threaded rod and heat the nut with Acetylene.

I would use a combination of heat and a drill.

Once you have removed the trailing arm from the subframe you will be able to attack both sides with ease - (assuming the other side is snapped flush) heating the snapped off bolt and then drill from the snapped side might push the bolt out of the hole (so if the shock was still in place it would be like trying the crew the bolt all the way through)

Stretch · #29 02-04-2015, 03:07 AM

Quote:

Originally Posted by steeleygreg

...
In the pic of the differential, can someone tell me what this electrical connector on the differential is and what is it for ?

That's your ABS sensor - ideally you should pull the sensor out of the differential before removing everything from the chassis! These sensors, however, can be a bit tight to remove and sensor damage may result.

What does the inside of you differential look like? Is it quite clean? If not removal of the sensor to check for muck might be worthwhile. Now is the time to get things cleaned out and ship shape.

Stretch · #30 02-04-2015, 03:23 AM

Note for later on after you've changed your trailing arm bushings =>

Make sure you align the trailing arms in such a position that the axles would be horizontal BEFORE you tighten the tralining arm bolts. To check this I find it is easiest to look though the wheel hub (no axle fitted!) and line that up by eye with the output shaft hole / flange on the differential.

Rear subframe removal and bushing replacement